Home Node Bs (HNBs) for Universal Mobile Telecommunications System (UMTS) and Home evolved Node Bs (HeNBs) for Long Term Evolution (LTE), hereinafter, interchangeably referred to as HNBs or HeNBs, have been introduced in LTE to increase the cellular coverage and the overall system throughput. The HNBs may have a dense deployment and may be in the coverage area of one or more macro Node Bs. For example, they may be used in a private house or in a coffee shop. An IDLE mode mobility (IDLE, cell paging channel (CELL_PCH), and URA_PCH for UMTS and IDLE for LTE) has been standardized. Standardizing a connected mode mobility (i.e., handover) for Release 9 has not been completed.
The HNB refers to a physical device that may be similar to a wireless local area network (WLAN) access point (AP). The HNB provides users with access to UMTS and/or LTE services over extremely small service areas, such as homes or small offices. The HNB is intended to connect to the operators' core network by using, for example, an internet connection (e.g., digital subscriber line (DSL)).
A HNB closed subscriber group (CSG) cell is a defined area over which radio coverage provided by the HNB may only be accessed by a group of subscribers authorized to use the services of the cell. The authorized wireless transmit/receive units (WTRUs) are called members of the CSG cell. The CSG may be a family or anyone in the vicinity of a particular location (e.g., anyone in a coffee shop) who attempts to access the HNB CSG cell. The subscriber (i.e., the WTRU) who may be an individual or an organization may deploy a CSG cell using a HNB over an area where such service is desired. Each WTRU stores a list, referred to herein as a white list or allowed list, which includes CSG identities (IDs) of the CSG cells it is authorized to access. A hybrid cell is a cell that works similar to a CSG cell for member WTRUs and similar to an open cell for non-member WTRUs, but may prioritize access for member WTRUs.
In wireless communication systems, various mobile devices, such as cell phones and other user equipment (UE), or a WTRU may be in connection with and served by a base station such as a HNB. A HeNB may serve as a base station/cell and may provide coverage over smaller areas than macro cells may provide in 3G, LTE, or other systems, for example.
FIG. 1 shows an example of a conventional HeNB deployment in a wireless communication system 100. The wireless communication system 100 includes an LTE macro cell 105, a 3GPP system cell 110, a higher network node (e.g., gateway) 115 and/or a mobility management entity (MME)/serving general packet radio service (GPRS) support node (SGSN) 120. The higher network node 115 is responsible for coordinating the operation of several HeNBs 125A, 125B and 125C. Alternatively, the MME/SGSN 120 may be responsible for coordinating the operation of HeNBs 125A, 125B and 125C. The MME is the LTE equivalent of a 3G/2G SGSN. The relationship between the LTE macro cell 105 and the 3GPP system 110, (e.g., wideband code division multiple access (WCDMA)/global system for mobile communications (GSM)), is that there may be areas where the coverage of these two technologies overlap. This overlap in coverage is similar to simultaneous coverage of GSM and WCDMA technologies. The higher network node 115 is likely to be a gateway function which interfaces with the MME/SGSN 120. As a gateway, the role of the higher network node 115 may be to act as a single macro cell towards the MME/SGSN 120 while supporting several small home cells.
FIG. 2 shows an LTE wireless communication system 200 including a WTRU 205, a serving CSG cell 210, and a neighbor CSG cell 215. To complete an inbound handover to a CSG cell in the LTE wireless communication system 200, the WTRU 205 needs to measure and report the CSG cell to the network. However, CSG cells are prone to physical layer cell identity (PCI) confusion, which is when two different CSG cells in the neighborhood of a radio network controller (RNC) or eNB, where the WTRU is initially connected, utilize the same PCI. PCI confusion may also exist if the WTRU has to handover to a CSG cell which it is not a member of (e.g., hybrid cell).
A HeNB may be an open node, a restricted access node, or a hybrid node, among others. A restricted access node HeNB may permit connection with a WTRU that is a member of a CSG of that node. In other words, if a restricted access HeNB node does not recognize the WTRU attempting to connect as a member of the node's CSG, the HeNB may not accept the connection, which may include a handover attempt from another HeNB. As indicated, an example of a restricted access HeNB may be a HeNB that belongs to a CSG. A CSG HeNB may provide access and service to a WTRU on a subscription (or membership) basis. Further, a CSG HeNB may be a CSG cell. A CSG cell may also include a CSG macro cell or CSG macro node B, among others. An open node or open HeNB may be a non-CSG cell.
The hybrid type HeNB may accept a connection with a WTRU that is not an identified member of the CSG to which the hybrid HeNB belongs, but the non-member WTRU connection with the hybrid HeNB may be subject to certain limitations. For example, the hybrid HeNB may deny the non-member WTRU a preferential rate or the non-member WTRU may be preempted before the member WTRU, should the hybrid HeNB need to preempt non-member WTRU due to a quality of service issue. A hybrid HeNB may be a hybrid cell. A hybrid cell may also include a hybrid macro cell or a hybrid node B, and the like.
At times, and for various reasons, a WTRU may need to transfer from one HeNB to another HeNB, or from one cell to another cell. For example, in a handover, a WTRU may replace a connection to one HeNB or cell with a connection to second HeNB cell. If the second HeNB is a CSG cell (or CSG HeNB, close mode cell, or CSG cell), the CSG cell may not accept a connection to a WTRU that the CSG cell does not recognize as a CSG member WTRU. In such situations, the handover may fail. A method and apparatus that allow the WTRU to search and add one or more CSG IDs in the WTRU white list while in connected mode are desired.